These experiments are designed to provide data which will permit a more complete description of the changes in visual cortex physiology that can be induced by limiting what an animal sees while it is developing. The visual environment of young kittens will be restricted in such a way that brain connections from one eye will have an advantage over those from the other eye early in life. Receptive fields of single cortical neurons will be studid for visual stimuli presented independently to the two eyes and cells will be categorized according to the relative strength of their responses for each eye. In one series of experiments, kittens will be reared with the eyelids of one eye sewn shut (monocular deprivation) and cortical cells will be studied while all input from the other eye is reversibly blocked by cooling the optic nerve. This will permit detailed comparison of cortical neuron responses for stimuli presented to the deprived eye when it alone is functionally connected to the brain and, following removal of cooling, when both eyes are connected. Other experiments will involve rearing animals with divergent strabismus and subtle manipulation of the timing of impulses coming to cortical cells from the two eyes during development in an effort to alter permanently the binocular connections of the visual cortex. This research will contribute to understanding the processes governing interaction between cortical input from the two eyes during development. The findings will relate to the problem of how sensory experience modifies the central nervous system and thus they will represent an important step towards uncovering the physiological basis of other readily modifiable brain functions such as learning and memory.